1. Field of the Invention
The present invention relates to a radio reception apparatus, and a method and a program for controlling adaptive array processing in the radio reception apparatus. More particularly, the present invention relates to a radio reception apparatus attaining a function to subject signals from a plurality of antennas to adaptive array processing, and a method and a program for controlling adaptive array processing in the radio reception apparatus.
2. Description of the Background Art
Recently, in a rapidly-developing mobile communication system (for example, Personal Handyphone System: hereinafter, referred to as xe2x80x9cPHSxe2x80x9d), a method of extracting a desired reception signal with adaptive array processing in a radio reception apparatus on a base station side or on a mobile terminal side during communication between the base station and the mobile terminal has been proposed.
In the adaptive array processing, based on a reception signal from a transmission station, a weight vector consisting of reception coefficients (weight) for each antenna in a reception station is calculated for adaptive control, whereby a signal from a desired transmission station is accurately extracted.
In a radio reception system in the reception station, a weight vector calculator calculating such a weight for each symbol in the reception signal is provided. The weight calculator usually performs processing to update a weight so as to reduce a square of an error between a known reference signal and the sum of complex multiplication of the reception signal by a calculated weight.
In the adaptive array processing, such a weight is adaptively updated (learning of weight) in accordance with time and fluctuation in a property of a propagation path for a signal radio wave, whereby an interfering component or noise is eliminated from the reception signal so as to extract the reception signal from a desired transmission station.
Technique for such adaptive array processing with MMSE as well as the RLS algorithm and the UWS algorithm with MMSE are well known, and described in detail, for example, in Nobuyoshi Kikuma, xe2x80x9cAdaptive Signal Processing by Array Antenna,xe2x80x9d Kagaku Gijutsu Shuppan, pp. 35-49, published on Nov. 25, 1998.
As described above, in the radio reception apparatus with a function of adaptive array processing, a desired signal having an interfering component or noise eliminated from a reception signal can be obtained.
On the other hand, in the radio reception apparatus with a function of adaptive array processing, adaptive array processing is always performed even when it is not necessary, such as when a desired signal can be obtained without adaptive array processing because the reception signal does not contain much interfering component or noise, or when the interfering component or noise in the reception signal cannot be eliminated even with the adaptive array processing.
Meanwhile, in the adaptive array processing, numerous operational processings are performed for a plurality of signals received at a plurality of antennas, resulting in large power consumption. As more power is consumed, a stand-by period or a continuous call time is shortened in particular in a radio reception apparatus on the mobile terminal side driven by a battery.
An object of the present invention is to provide a radio reception apparatus capable of avoiding unnecessary power consumption as a result of unnecessary adaptive array processing, as well as a method and a program for controlling adaptive array processing in the radio reception apparatus.
According to one aspect of the present invention, a radio reception apparatus includes: a plurality of antennas; RF reception units provided corresponding to each antenna and performing amplification and frequency conversion of signals received at each antenna; an adaptive array operational processing unit performing adaptive array operational processing on signals output from the plurality of RF reception units; and a control unit. The control unit selects from a first mode in which adaptive array processing is performed and a second mode in which adaptive array processing is not performed, in accordance with a prescribed condition. When the first mode is selected, the control unit performs first control to operate the plurality of RF reception units and the adaptive array operational processing unit. When the second mode is selected, the control unit performs second control so that one RF reception unit is selected as a first RF reception unit to operate and an operation of an RF reception unit other than the first RF reception unit and the adaptive array operational processing unit is stopped.
Preferably, each RF reception unit further detects a level of a reception signal received at a corresponding antenna, and outputs the detected reception signal level to the control unit. The control unit selects the first mode when a difference between a highest level and a lowest level among the detected reception signal levels is not larger than a prescribed value, and selects the second mode when the difference between the highest level and the lowest level is larger than the prescribed value.
Preferably, each RF reception unit further detects a level of a reception signal received at a corresponding antenna, and outputs the detected reception signal level to the control unit. The control unit selects the first mode when all reception signal levels of the detected reception signal levels are lower than a prescribed value, and selects the second mode when a level of at least one reception signal is not lower than the prescribed value.
Preferably, the radio reception apparatus further includes a demodulation unit demodulating a signal processed by the adaptive array operational processing unit while the first mode is selected, and a communication quality calculating unit calculating communication quality based on the demodulated signal. While the first mode is selected, the control unit maintains the first mode when communication quality is not higher than prescribed quality, and selects the second mode when the communication quality is higher than the prescribed quality.
Preferably, the radio reception apparatus further includes a demodulation unit demodulating a signal processed by the first RF reception unit and not processed by the adaptive array operational processing unit while the second mode is selected, and a communication quality calculating unit calculating communication quality based on the demodulated signal. While the second mode is selected, the control unit selects the first mode when communication quality is not higher than prescribed quality, and maintains the second mode when the communication quality is higher than the prescribed quality.
Preferably, the radio reception apparatus further includes an input portion through which selection from the first mode and the second mode is input by user manipulation. The control unit selects the first mode when selection of the first mode is input through the input portion, and selects the second mode when selection of the second mode is input through the same.
Preferably, each RF reception unit further detects a level of a reception signal received at a corresponding antenna, and outputs the detected reception signal level to the control unit. The control unit selects as a first RF reception unit, an RF reception unit that has output a level highest among the detected reception signal levels when the second mode is selected.
Preferably, the control unit selects a predetermined RF reception unit as a first RF reception unit when the second mode is selected.
According to another aspect of the present invention, a method of controlling adaptive array processing in a radio reception apparatus which includes a plurality of antennas, RF reception units provided corresponding to each antenna and performing amplification and frequency conversion of signals received at each antenna, and an adaptive array operational processing unit performing adaptive array operational processing on signals output from the plurality of RF reception units, includes the steps of: selecting from a first mode in which adaptive array processing is performed and a second mode in which adaptive array processing is not performed, in accordance with a prescribed condition; and performing control in which, when the first mode is selected, first control is performed to operate the plurality of RF reception units and the adaptive array operational processing unit, and when the second mode is selected, second control is performed so that one RF reception unit is selected as a first RF reception unit to operate and that an operation of an RF reception unit other than the first RF reception unit and the adaptive array operational processing unit is stopped.
Preferably, the method of controlling adaptive array processing further includes the step of detecting a level of a reception signal received at a corresponding antenna. In the step of selecting, the first mode is selected when a difference between a highest level and a lowest level among the detected reception signal levels is not larger than a prescribed value, and the second mode is selected when the difference between the highest level and the lowest level is larger than the prescribed value.
Preferably, the method of controlling adaptive array processing further includes the step of detecting a level of a reception signal received at a corresponding antenna. In the step of selecting, the first mode is selected when all reception signal levels of the detected reception signal levels are lower than a prescribed value, and the second mode is selected when a level of at least one reception signal is not lower than the prescribed value.
Preferably, the method of controlling adaptive array processing further includes the steps of demodulating a signal processed by the adaptive array operational processing unit while the first mode is selected, and calculating communication quality based on the demodulated signal. In the step of selecting, while the first mode is selected, the first mode is maintained when communication quality is not higher than prescribed quality, and the second mode is selected when the communication quality is higher than the prescribed quality.
Preferably, the method of controlling adaptive array processing further includes the steps of demodulating a signal processed by the first RF reception unit and not processed by the adaptive array operational processing unit while the second mode is selected, and calculating communication quality based on the demodulated signal. In the step of selecting, while the second mode is selected, the first mode is selected when communication quality is not higher than prescribed quality, and the second mode is maintained when the communication quality is higher than the prescribed quality.
Preferably, the method of controlling adaptive array processing further includes the step of inputting selection from the first mode and the second mode by user manipulation. In the step of selecting, the first mode is selected when selection of the first mode is input, and the second mode is selected when selection of the second mode is input.
Preferably, the method of controlling adaptive array processing further includes the step of detecting a level of a reception signal received at a corresponding antenna. In the step of controlling, when the second mode is selected, an RF reception unit that has output a level highest among the detected reception signal levels is selected as a first RF reception unit.
Preferably, in the controlling step, a predetermined RF reception unit is selected as a first RF reception unit when the second mode is selected.
According to yet another aspect of the present invention, a program for controlling adaptive array processing in a radio reception apparatus which includes a plurality of antennas, RF reception units provided corresponding to each antenna and performing amplification and frequency conversion of signals received at each antenna, and an adaptive array operational processing unit performing adaptive array operational processing on signals output from the plurality of RF reception units, causes a computer to execute the steps of: selecting from a first mode in which adaptive array processing is performed and a second mode in which adaptive array processing is not performed, in accordance with a prescribed condition; and performing control in which, when the first mode is selected, first control is performed to operate the plurality of RF reception units and the adaptive array operational processing unit, and when the second mode is selected, second control is performed so that one RF reception unit is selected as a first RF reception unit to operate and that an operation of an RF reception unit other than the first RF reception unit and the adaptive array operational processing unit is stopped.
Preferably, each RF reception unit further detects a level of a reception signal received at a corresponding antenna. In the step of selecting, the first mode is selected when a difference between a highest level and a lowest level among the detected reception signal levels is not larger than a prescribed value, and the second mode is selected when the difference between the highest level and the lowest level is larger than the prescribed value.
Preferably, each RF reception unit further detects a level of a reception signal received at a corresponding antenna. In the step of selecting, the first mode is selected when all reception signal levels of the detected reception signal levels are lower than a prescribed value, and the second mode is selected when a level of at least one reception signal is not lower than the prescribed value.
Preferably, the program for controlling adaptive array processing further causes a computer to execute the steps of demodulating a signal processed by the adaptive array operational processing unit while the first mode is selected, and calculating communication quality based on the demodulated signal. In the step of selecting, while the first mode is selected, the first mode is maintained when communication quality is not higher than prescribed quality, and the second mode is selected when the communication quality is higher than the prescribed quality.
As described above, the present invention can avoid unnecessary power consumption as a result of unnecessary adaptive array processing.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.